Route guide information delivery method, route guidance method, information terminal and information delivery center

ABSTRACT

Upon receiving a request from a vehicle-mounted device  100,  a distribution center  200  executes a recommend route calculation and a guide calculation and transmits recommended route information and the data size of guide information to the vehicle-mounted device  100.  The vehicle-mounted device  100  calculates the estimated download time based upon the size of the guide information and displays it. If the driver requests a split download, the vehicle-mounted device  100  outputs a split-download instruction to the distribution center  200.  The distribution center  200  transmits to the vehicle-mounted device  100  guide information to be used to guide the vehicle from the start point to the first guidance-requiring intersection. While executing the route guide processing, the vehicle-mounted device  100  downloads the remaining guide information in the background.

INCORPORATION BY REFERENCE

The disclosure of the following priority application is hereinincorporated by reference:

-   Japanese Patent Application No. 2002-348207 filed Nov. 29, 2002

TECHNICAL FIELD

The present invention relates to a technology for exchanging informationused to provide route guidance between an information terminal deviceand an information distribution center.

BACKGROUND ART

There is a technology known in the related art with which routeinformation and guide information obtained through arithmetic operationsand transmitted from a guide information distribution center to a mobilerecipient such as a vehicle are used by a vehicle-mounted informationterminal device to guide the vehicle along the route based upon thereceived guide information. In conjunction with the guide informationdistribution center and the vehicle-mounted information terminal deviceused in the related art, a route search request transmitted from thevehicle side is received at the guide information distribution centerand the route information and the guide information obtained at theguide information distribution center through arithmetic operationsexecuted in response to the route search request are transmitted to thevehicle side (see, for instance, patent reference literature 1). Whenthe vehicle is currently located a great distance from the destination,the data size of the guide information calculated at the guideinformation distribution center is bound to be very large. This givesrise to a problem in that since it takes a long time to receive theinformation at the vehicle, the route guidance for the user cannot bestarted immediately by the vehicle-mounted information terminal device.

The present invention provides a route guide information distributionmethod for split-distributing data with a large volume so as to firstdistribute only the data that are initially needed, a route guidancemethod for providing route guidance based upon the split-distributeddata, an information terminal that starts route guidance by using thesplit-distributed data and an information distribution center thatdistributes only the data that are initially needed by splitting theentirety of the data.

DISCLOSURE OF THE INVENTION

According to the 1st invention, in a method for distributing route guideinformation to be used when providing route guidance based uponinformation related to a recommended route from a start point to adestination and exchanged between an information terminal and aninformation distribution center, the information distribution center:receives information indicating the start point and the destination fromthe information terminal; obtains through a search calculation routeguide information for a route from the start point to the destination;and splits results of the search calculation and transmits the resultsin installments to the information terminal.

According to the 2nd invention, in a route guidance method for providingroute guidance based upon information related to a recommended routefrom a start point to a destination and exchanged between an informationterminal and an information distribution center, the informationterminal: transmits information indicating the start point and thedestination to the information distribution center; and starts the routeguidance upon receiving an installment of search calculation results foran area near the start point transmitted thereto by splitting results ofa search calculation executed at the information distribution center toobtain route guide information.

According to the 3rd invention, in a route guidance method for providingroute guidance based upon information related to a recommended routefrom a start point to a destination and exchanged between an informationterminal and an information distribution center by executing in sequencesteps (a) to (d) below: (a) the information terminal transmitsinformation indicating the start point and the destination to theinformation distribution center; (b) the information distribution centerobtains route guide information for a route from the start point to thedestination by executing a search calculation; (c) the informationdistribution center splits results of the search calculation andtransmits the search calculation results to the information terminal ininstallments; and (d) the information terminal starts route guidanceupon receiving, at least, a search calculation results installmentcorresponding to an area near the start point.

In the route guidance method according to the 3rd invention, when astate of communication between the information terminal and theinformation distribution center is poor, the information distributioncenter can split the search calculation results and transmit the searchcalculation results to the information terminal in installments. Also,in the route guidance method according to the 3rd invention, when adistance between the start point and the destination is equal to orgreater than a predetermined value, the information distribution centercan split the search calculation results and transmit the searchcalculation results to the information terminal in installments. Or, inthe route guidance method according to the 3rd invention, when acommunication device with a data transmission speed equal to or lowerthan a predetermined value is connected to the information terminal, theinformation distribution center can split the search calculation resultsand transmit the search calculation results to the information terminalin installments.

According to the 4th invention, in a route guidance method for providingroute guidance by causing an information terminal, which transmitsinformation indicating a start point and a destination to an informationdistribution center, and the information distribution center obtainsroute guide information for a route from the start point to thedestination through a search calculation and transmits results of thesearch calculation to the information terminal in installments bysplitting the search calculation results if a specific condition exists,to execute in sequence steps (a) to (d) below: (a) a user is informed ofan estimated download time for downloading the search calculationresults, determined based upon a physical quantity indicating a size ofthe search calculation results; (b) the information terminal transmitsto the information distribution center information indicating aninstruction by the user that the information distribution center splitthe search calculation results and transmit the search calculationresults in installments; (c) upon receiving the information indicatingthe instruction by the user that the search calculation results be splitand transmitted in installments, the information distribution centerextracts search calculation results corresponding to an area near thestart point from the search calculation results and transmits theextracted search calculation results; and (d) upon receiving the searchcalculation results corresponding to the area near the start point, theinformation terminal starts the route guidance.

In the route guidance method according to the 4th invention, the searchcalculation results include route information of the route from thestart point to the destination and guide information used to indicate anadvancing direction or the like at each guide point on the route. Inthis case, the search calculation results corresponding to the area nearthe start point include at least guide information for a block extendingfrom the start point to a next guide point. It is preferred that thephysical quantity indicates a data size of the guide information or anumber of guide points contained in the guide information. Afterstarting the route guidance, the information terminal may transmit arequest to the information distribution center for remaining guideinformation. Or, the information terminal may transmit a request to theinformation distribution center for the remaining guide information tobe distributed in units each corresponding to a guide point; and eachtime the request is received, the information distribution center maytransmit guide information extracted in a unit corresponding to a guidepoint to the information terminal.

According to the 5th invention, a distribution center that distributesroute guide information to be used to enable an information terminal toprovide route guidance, which is obtained based upon information relatedto a recommended route from a start point to a destination and exchangedwith the information terminal, comprises: a receiving means forreceiving a route search request that a route from the start point tothe destination be searched, which is transmitted from the informationterminal; a search calculation means for obtaining route guideinformation for the route from the start point to the destination byexecuting a search calculation in response to the request; an extractionmeans for extracting search calculation results corresponding to an areanear the start point from the search calculation results obtainedthrough the search calculation executed by the search calculation means;and a transmission means for first transmitting the results extracted bythe extraction means to the information terminal and then transmittingremaining search calculation results to the information terminal.

According to the 6th invention, an information terminal that providesroute guidance by exchanging information related to a recommended routefrom a start point to a destination with an information distributioncenter, comprises: a transmission/reception means for transmittinginformation indicating the start point and the destination to theinformation distribution center and receiving search calculation resultsconstituting route guide information obtained through an arithmeticoperation executed at the information distribution center; and aguidance starting means for starting the route guidance upon receivingat least search results corresponding to an area near the start pointand constituting part of the route guide information obtained throughthe arithmetic operation executed at the information distributioncenter, split and transmitted in installments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the overall configuration of an embodiment that includesthe information terminal and the information distribution centeraccording to the present invention;

FIG. 2 is a system block diagram of the information terminal accordingto the present invention;

FIG. 3 shows the structure of the map data displayed at the informationterminal according to the present invention;

FIG. 4 shows the structure of the data used in a route search executedat the information distribution center according to the presentinvention;

FIG. 5 presents a flowchart of the operations executed at theinformation terminal and the information distribution center accordingto the present invention;

FIG. 6 shows the display monitor at the information terminal accordingto the present invention, on which the current vehicle position isindicated in a road map;

FIG. 7 shows a subroutine that may be executed in step S100 in theflowchart presented in FIG. 5;

FIG. 8 shows the display monitor at the information terminal accordingto the present invention, on which a destination is set;

FIG. 9 shows the display monitor at the information terminal accordingto the present invention, on which route search conditions aredisplayed;

FIG. 10 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that a routesearch is in progress is displayed;

FIG. 11 shows a subroutine that may be executed in step S700 in theflowchart presented in FIG. 5;

FIG. 12 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5;

FIG. 13 shows the display monitor at the information terminal accordingto the present invention, with an inquiry to the user as to whether ornot the guide information is to be split-downloaded;

FIG. 14 shows the display monitor at the information terminal accordingto the present invention, with a display brought up while the guideinformation is split-downloaded in the background;

FIG. 15 shows a subroutine that may be executed in step S700 in theflowchart presented in FIG. 5;

FIG. 16 shows the display monitor at the information terminal accordingto the present invention, with an inquiry to the user as to whether ornot the guide information is to be split-downloaded;

FIG. 17 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5;

FIG. 18 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that the guideinformation is to be split-downloaded is displayed;

FIG. 19 shows a subroutine that may be executed in step S100 in theflowchart presented in FIG. 5;

FIG. 20 shows a subroutine that may be executed in step S700 in theflowchart presented in FIG. 5;

FIG. 21 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5;

FIG. 22 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that the guideinformation is to be split-downloaded is displayed;

FIG. 23 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5;

FIG. 24 shows a subroutine that may be executed in step S100 in theflowchart presented in FIG. 5;

FIG. 25 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that the guideinformation is to be split-downloaded is displayed;

FIG. 26 shows a subroutine that may be executed in step S100 in theflowchart presented in FIG. 5;

FIG. 27 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5;

FIG. 28 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that guidance tothe first waypoint is now starting is displayed;

FIG. 29 shows the display monitor at the information terminal accordingto the present invention, with an inquiry to the user as to whether ornot the route search information to the next waypoint is to bedownloaded;

FIG. 30 shows the display monitor at the information terminal accordingto the present invention, on which a message indicating that the routesearch information to the next waypoint is to be downloaded;

FIG. 31 shows a subroutine that may be executed in step S200 in theflowchart presented in FIG. 5; and

FIG. 32 presents a flowchart of the operations executed at theinformation terminal and the information distribution center in aseventh embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

In reference to FIGS. 1 to 14, the first embodiment achieved by adoptingthe information terminal (or the information terminal device) accordingto the present invention in a car navigation system (hereafter referredto as a vehicle-mounted device) 100 is explained. FIG. 1 shows thevehicle-mounted device 100 achieved in the first embodiment, adistribution (or delivery) center 200 that distributes or delivers mapinformation and route search information to the vehicle-mounted device100, a portable telephone 150 used to exchange various types of databetween the vehicle-mounted device 100 and the distribution center 200and a mobile communication network 250. As shown in FIG. 1, the portabletelephone 150 is connected to the vehicle-mounted device 100. Thevehicle-mounted device 100 is able to transmit a request for detailedmap information, route information and guide information needed forroute guidance to the distribution center 200 from the portabletelephone 150 via the mobile communication network 250. It is alsocapable of receiving at the portable telephone 150 the detailed mapinformation, the route information and the guide information transmittedfrom the distribution center 200 via the mobile communication network250. It is to be noted that a car phone, a communication LAN or acommunication device provided for exclusive use in conjunction with thevehicle-mounted device may be utilized instead of the portable telephone150.

FIG. 2 is a system block diagram showing the structure of thevehicle-mounted device 100. Reference numeral 111 in FIG. 2 indicates acurrent position detection device that detects the current position ofthe vehicle, which may be constituted with, for instance, an azimuthsensor 111 a for detecting the advancing azimuth of the vehicle, avehicle speed sensor 111 b for detecting the vehicle speed and a GPSsensor 111 c for detecting a GPS signal transmitted from a GPSsatellite. Reference numeral 112 indicates a memory card used to storesimplified road map display data for the entire nation and road mapdisplay data having been received, which is constituted with anon-volatile semiconductor memory and can be detachably loaded into thevehicle-mounted device 100. Reference numeral 114 indicates a controlcircuit that implements overall control of the device and is constitutedwith a microprocessor and its peripheral circuits. The control circuit114 uses a RAM 115 as its work area when implementing various types ofcontrol to be detailed later by executing a control program stored in aROM 116.

Reference numeral 117 indicates an input device having various switchesthrough which the destination for the vehicle and the like are input.Reference numeral 118 indicates an image memory in which image data usedto display images at a display monitor 119 are stored. The image dataare generated by using road map drawing data, various types of graphicdata and the like. The image data stored in the image memory 118 areread out as needed to be used for an image display at the displaymonitor 119. At the display monitor 119, route information and guideinformation are displayed together with a road map.

The vehicle-mounted device 100 structured as described above executesvarious types of navigation based upon the subject vehicle positioninformation provided by the current position detection device 111 andthe various types of data stored in the memory card 112. For instance,it displays a road map of an area around the subject vehicle positionhaving the subject vehicle position indicated therein at the displaymonitor 119 and guides the driver based upon the route information andthe guide information downloaded from the distribution center 200.

A request receiving server at the distribution center 200 in FIG. 1,which is indicated by reference numeral 201, receives the subjectvehicle position information and a map•route distribution request fromthe vehicle-mounted device 100 and executes processing as requested.Reference numeral 202 indicates a map•POI server having stored therein adetailed roadmap and POI information (point of interest: informationregarding site-seeing spots and various types of facilities) for theentire nation, which outputs data to the request receiving server 201 inresponse to a request issued by the request receiving server 201.Reference numeral 203 indicates a search•guide server that executesarithmetic operations for route search and route guidance in response toa request from the request receiving server 201 and outputs the resultsof the arithmetic operations (recommended route information) to therequest receiving server 201. Reference numeral 204 indicates a customerDB server. The map•POI data or the results of the arithmetic operationsfor the route search and the route guidance requested by thevehicle-mounted device 100 are a first stored into the customer DBserver 204 in correspondence to the specific customer's vehicle-mounteddevice 100 and are then distributed to the vehicle-mounted device 100via the request receiving server 201. Each vehicle-mounted device 100 ispreassigned with an ID code used to identify the subject vehicle, andvarious types of information are stored in a storage area allocated incorrespondence to the ID code at the customer DB server 204.

Data Structures

FIGS. 3(a) and 3(b) show the structure of the map data used for mapdisplay at the vehicle-mounted device 100. The map data are link stringdata grouped in correspondence to individual mesh areas each assignedwith a mesh code and stored. It is to be noted that a data structure isadopted for the link string data in which each road is expressed byusing nodes such as intersections and links connecting the individualnodes. The term “mesh areas” refers to equally divided blocks of theroad map. A number used to identify the subject mesh area is stored in amesh code storage area 401. In a link string data storage area 402, thepositional coordinates X and Y of each node, link numbers of the linkspresent between the nodes and the positional coordinates X and Y ofinterpolation points further dividing the links into shorter segmentsare stored in their respective storage areas, as shown in FIG. 3(b).These positional coordinates are used as shape data in the map displayand locator processing.

FIG. 4 shows the structure of the route search data. Unlike the mapdata, the route search data are constituted with branching pointinformation, intersection information and the like which do not beardirect relevance to road shapes. As shown in FIG. 4, in correspondenceto each point (node) connecting links each of which is the smallest unitof data used to express a road, node information indicating connectingrelations with other nodes is stored. Each set of node informationcontains subject node information and adjacent node information with thepositional coordinates of the subject node stored in the subject nodeinformation. As adjacent node information corresponding to a givenadjacent node, the adjacent node number, the number assigned to the linkconnecting the subject node to the adjacent node, the link cost of thelink and traffic control information with regard to the link are storedas shown in the figure. In addition, the individual sets of nodeinformation are stored in the order matching the order in which thelinks are connected and, as a result, the node number of a given subjectnode can be ascertained based upon the order in which the set of nodeinformation is stored.

The route search calculation is executed by using the route search datadescribed above. Route guide data resulting from the route search arecreated by extracting the nodes present on the recommended route fromthe start point to the destination from the route search data through aknown method. The Route guide data include guide point data. The guidepoint data are constituted with offset data for enlarged intersectionarea map data and audio data. When guiding the vehicle along the route,these offset data are referenced as the vehicle reaches a point severalhundred meters from a guide point to display an enlarged intersectionarea map on the display monitor and output the audio data through aspeaker, thereby providing the driver with route guidance. Namely, theroute information mentioned earlier is constituted with recommendedroute data indicating the recommended route with a plurality of nodesand the guide information mentioned earlier is constituted with guidepoint data, i.e., the enlarged map data and the audio data obtained byreferencing the offset data.

In conjunction with the data structured as described above, uponreceiving a route search request and a detailed map request as well asthe information indicating the current vehicle position, a waypoint anda destination transmitted from the vehicle-mounted device 100, thedistribution center 200 executes a recommended route calculation and aguide calculation based upon the information received from thevehicle-mounted device 100. Then, the recommended route information andthe guide information resulting from the calculations and the detailedmap information are transmitted from the distribution center 200 to thevehicle-mounted device 100. Based upon the recommended routeinformation, the guide information and the detailed map informationreceived from the distribution center 200, the vehicle-mounted device100 is able to guide the vehicle along the route. However, if thevehicle is currently located a great distance away from the destination,the volume of the transmission data is bound to be very large and itwill take a long time for the vehicle-mounted device 100 to receive allthe information and start providing guidance. Accordingly, the guideinformation is split-downloaded (i.e. is divided and downloaded) asdescribed below in the first embodiment.

-   (1) The distribution center 200 transmits to the vehicle-mounted    device 100 the route information of the route extending from the    start point to the destination, which results from the search    calculation, and also transmits information indicating the data size    of the guide information to be downloaded to the vehicle-mounted    device 100.-   (2) The vehicle-mounted device 100 displays the entire route from    the start point to the destination at the monitor. At this time, the    vehicle-mounted device 100 calculates the estimated download time    based upon the size of the guide information to be downloaded and    prompts the driver to decide whether or not to split-download the    guide information by bringing up the estimated download time on    display.-   (3) If the driver requests a split download, the vehicle-mounted    device 100 outputs a split-download instruction to the distribution    center 200.-   (4) The distribution center 200 transmits to the vehicle-mounted    device 100 guide information to be used to guide the vehicle from    the start point to the first guidance-requiring intersection and the    route guidance starts.-   (5) While executing the route guide processing, the vehicle-mounted    device 100 downloads the remaining guide information in units of    individual guidance-requiring intersections in the background.

The present invention is explained in further detail below in referenceto an example in which the necessary detailed map data are alreadystored in the memory card 112 at the vehicle-mounted device 100 and theroute search request is transmitted to the distribution center 200.

Description in Reference to the Flowcharts

FIG. 5 presents a flowchart of the operations executed by thevehicle-mounted device 100, the request receiving server 201, thesearch•guide server 203 and the customer DB server 204. The operationalflow in FIG. 5 is achieved by executing the processing program for thevehicle-mounted device 100 at the control circuit 114, executing theprocessing program for the request receiving server 201 at the requestreceiving server 201, executing the processing program for thesearch•guide server 203 at the search•guide server 203 and executing theprocessing program for the customer DB server 204 at the customer DBserver 204.

As the ignition key is set to an accessory on (ACC ON) position, powerto the vehicle-mounted device 100 is turned on and the program thatenables the vehicle-mounted device 100 to execute the processing shownin FIG. 5 is started up. In step S1, a map of an area around thevehicle, which had been on display immediately before thevehicle-mounted device 100 was turned off most recently, is brought upon display as an initial screen. In step S3, the current vehicleposition is measured or detected. After deciding that the subjectvehicle position has been measured in step S5, the operation proceeds tostep S7 to indicate the current vehicle position in a map of an areaaround the current vehicle position at the display monitor 119 as shownin FIG. 6 before the operation proceeds to step S100. Reference numeral401 in FIG. 6 indicates a subject vehicle position mark. In step S100, asearch request for a route from the current vehicle position to adestination is transmitted to the distribution center 200 before theoperation proceeds to step S11. The arithmetic operation subroutineexecuted in step S100 is to be described in detail later. In step S11,the operation waits in standby for the reception of route searchinformation having been requested through the subroutine in step S100.

At the distribution center 200, upon receiving the route search requestfrom the vehicle-mounted device 100 in step S51, the operation proceedsto step S53 to transmit a request reception parameter to the customer DBserver 204 and then the operation proceeds to step S55. In step S55, aroute search request is transmitted to the search•guide server 203 basedupon the route search request issued by the vehicle-mounted device 100.

At the search•guide server 203, upon receiving the route search requestfrom the request receiving server 201 in step S71, the operationproceeds to step S700 to execute a recommended route calculation and aguide calculation and then the operation proceeds to step S73. Thearithmetic operation subroutine executed in step S700 is to be describedin detail later. In step S73, route information and guide informationresulting from the arithmetic operations are transmitted to the requestreceiving server 201.

At the request receiving server 201, upon receiving the arithmeticoperation results from the search guide•server 203 in step S57, theoperation proceeds to step S59 to transmit the results of the arithmeticoperations executed by the search•guide server 203 to the customer DBserver 204 before the operation proceeds to step S61. In step S61, thefull route information and the data size of the guide information amongthe arithmetic operation results provided by the search•guide server 203are transmitted to the vehicle-mounted device 100.

At the customer DB server 204, after receiving the request receptionparameter in step S81, the results of the arithmetic operations havingbeen executed at the search•guide server 203, which have been receivedfrom the request receiving server 201, are stored into the storage areaallocated in correspondence to the ID number of the vehicle-mounteddevice 100.

After deciding that the route information and the information indicatingthe data size of the guide information provided by the distributioncenter 200 have been received in step S11, the operation at thevehicle-mounted device 100 proceeds to the subroutine in step S200 toexecute guide processing. Instep S200, a request for the guideinformation that has not yet been received is transmitted to thedistribution center 200. Upon receiving the guide information, the guideprocessing is started based upon the received guide information. It isto be noted that the arithmetic operation subroutine executed in stepS200 is to be described in detail later.

The following is a detailed explanation of the operational flow throughwhich the route search request is transmitted from the vehicle-mounteddevice 100 to the distribution center 200 and the guide processing iseventually executed. As explained earlier, the information initiallytransmitted from the distribution center 200 to the vehicle-mounteddevice 100 in the first embodiment includes the information indicatingthe data size of the guide information as well as the route information.Thus, the user is able to choose whether or not the guide informationyet-to-be received should be split-downloaded from the distributioncenter 200 based upon the data size of the guide information and theestimated download time calculated by the vehicle-mounted device 100.

FIG. 7 presents an example of a subroutine that may be executed in stepS100 in the first embodiment. Through this subroutine processing, aspecific condition to be indicated in the route search requesttransmitted from the vehicle-mounted device 100 to the distributioncenter 200 is determined. As the current vehicle position is indicatedat the display monitor 119 as shown in FIG. 6 in step S7 in the mainroutine shown in FIG. 5, the operation proceeds to execute thesubroutine in step S100. In step S101, the operation waits in standbyfor the user to set a destination through a specific operation. A FIG. 8shows a display brought up on the display monitor 119 to indicate thedestination having been set. A point 402 at which the lines extendingperpendicular to each other cross in the display at the display monitor119 indicates the destination. After deciding in step S101 that adestination has been set, the operation proceeds to step S103 to displaythe search condition setting screen shown in FIG. 9. A specificcondition to be applied when the distribution center 200 executes theroute search, which is selected by the user, is set as the searchcondition. The selection may be made from, for instance, the followingconditions.

-   (1) The route search is to be executed by giving priority to toll    roads.-   (2) The route search is to be executed by giving priority to regular    roads.-   (3) The route search is to be executed so as to minimize the    traveling time.-   (4) The route search is to be executed so as to minimize the    traveling distance.

Upon deciding in step S105 that the search condition has been set, thedisplay with a message indicating that the search is in progress shownin FIG. 10 is brought up at the display monitor 119, and then theoperation proceeds to step S111. If it is decided in step S111 that thesearch condition having been set by the user in steps S103 through S105gives priority to toll roads, the operation proceeds to step S113. Instep S113, a route search request indicating the search condition givingpriority to toll roads as well as the current position and thedestination is transmitted to the distribution center 200, and then theoperation returns to the main routine to execute the main routineprocessing in step S11 and subsequent steps.

If, on the other hand, it is decided in step S111 that the searchcondition having been set by the user in steps S103 through S105 doesnot give priority to toll roads, the operation proceeds to step S121. Ifit is decided in step S121 that the search condition having been set bythe user in steps S103 through S105 gives priority to regular roads, aroute search request indicating the search condition giving priority toregular roads as well as the current position and the destination istransmitted to the distribution center 200 in step S123 before theoperation returns to the main routine to execute the main routineprocessing in step S11 and subsequent steps.

If, on the other hand, it is decided in step S121 that the searchcondition having been set by the user in steps S103 through S105 doesnot give priority to regular roads, the operation proceeds to step S131.If it is decided in step S131 that the search condition having been setby the user in steps S103 through S105 gives priority to minimizetraveling time, a route search request indicating the search conditiongiven priority to minimized traveling time as well as the currentposition and the destination is transmitted to the distribution center200 in step S133 before the operation returns to the main routine toexecute the main routine processing in step S11 and subsequent steps.

If it is decided in step S131 that the search condition having been setby the user in steps S103 through S105 does not give priority tominimized traveling time, the operation proceeds to step S143 totransmit a route search request indicating the search condition givingpriority to minimized traveling distance as well as the current positionand the destination to the distribution center 200 before the operationreturns to the main routine to execute the main routine processing instep S11 and subsequent steps.

Thus, the information indicating the current vehicle position and thedestination and the route search condition determined through thesubroutine is transmitted to the distribution center 200 together withthe ID number used to identify the vehicle. As explained earlier, uponreceiving these data, the distribution center 200 accesses thesearch•guide server 203 to execute the route calculation in step S700 inFIG. 5.

FIG. 11 shows the subroutine executed in step S700 in the firstembodiment. As the search•guide server 203 receives the route searchrequest from the request receiving server 201 in step S71 in FIG. 5, theoperation proceeds to step S700. In step S701 a, the route searchcalculation is executed based upon the position information and theroute search condition having been transmitted from the vehicle-mounteddevice 100. In step S703 a, a route coordinate string is extracted fromthe recommended route resulting from the route search calculation. Theroute coordinate string contains the positional coordinates X and Y of aplurality of nodes present in the roads on the recommended route. Instep S705 a, the size (data volume) of the guide information iscalculated based upon the results of the calculation having beenexecuted in step S701 a. In step S707 a, the data indicating the guideinformation size calculated in step S705 a are appended to the routeinformation (the route coordinate string data having been obtained instep S703 a) to be transmitted to the vehicle-mounted device 100, beforethe operation returns to the main routine. Then, in step S73 in the mainroutine, the route information and the guide information obtainedthrough the arithmetic operations executed in the subroutine in stepS700 are transmitted to the request receiving server 201.

As explained earlier, the request receiving server 201 first transmitsthe arithmetic operation results received from the search•guide server203 to the customer DB server 204 in step S59 and then the operationproceeds to step S61. In step S61, the request receiving server 201transmits the route information having the guide information size dataattached thereto to the vehicle-mounted device 100.

At the vehicle-mounted device 100, upon deciding in step S11 that theroute information provided by the distribution center 200 has beenreceived, the operation proceeds to the subroutine in step S200.

FIG. 12 shows the subroutine executed in step S200 in the firstembodiment. Through this subroutine processing, the guide information isreceived and used for route guidance. In step S251, an estimateddownload time required to receive all the guide information iscalculated. This calculation is executed through the followingprocedure. First, the effective download speed at which the routeinformation received from the distribution center 200 has beendownloaded is calculated by dividing the route information size by thelength of time having been spent downloading the route information.Then, the estimated download time is calculated by dividing the size ofthe yet-to-be received guide information, which is indicated in thedownloaded information, by the effective download speed.

In step S253, the route information having been received in step S11 andthe estimated download time having been calculated in step S251 arebrought up on display at the display monitor 119. FIG. 13 shows thescreen brought up on display at the display monitor 119 in step S253. Asshown in FIG. 13, a bold line 301 indicating the recommended route and adialogue 302 asking the user whether or not the yet-to-be received guideinformation is to be split-downloaded are displayed at the displaymonitor 119. Through the dialogue 302, which includes indicated thereinthe guide information size and the estimated download time having beencalculated in step S251, the user is asked whether or not he wishes tosplit-download the guide information.

In step S255, a decision is made with regard to the download methodselected by the user, through which the yet-to-be received guideinformation is to be downloaded. If it is decided in step S255 that theuser has opted for a split download, the operation proceeds to step S257to transmit a split-download request to the distribution center 200. If,on the other hand, it is decided in step S255 that the user has notopted for a split download, the operation proceeds to step S259 totransmit to the distribution center 200 a request for downloading theyet-to-be received guide information all at once in a batch.

In step S63 in FIG. 5, the request receiving server 201 outputs arequest for the customer DB server 204 to transmit part of or all of theyet-to-be transmitted guide information stored therein in response tothe distribution request from the vehicle-mounted device 100. Inresponse to the request from the request receiving server 201, which isreceived in step S85, i.e., in response to the distribution request fromthe vehicle-mounted device 100, the customer DB server 204 transmits tothe request receiving server 201 part of the yet-to-be transmitted guideinformation stored therein or all the yet-to-be transmitted guideinformation stored therein in step S87. The request receiving server 201transmits the yet-to-be transmitted guide information received from thecustomer DB server to the vehicle-mounted device 100 in step S65.

When the customer DB server 204 transmits the yet-to-be transmittedguide information stored therein in divided installments in response tothe request from the request receiving server 201 having been receivedin step S85, i.e., in response to the distribution request from thevehicle-mounted device 100, the guide information is divided incorrespondence to individual guidance-requiring intersections. If thedistances between guidance-requiring intersections are small, the guideinformation should be divided so as to allow a plurality ofguidance-requiring intersections to be included in a single dividedblock of guide information.

In step S261 in FIG. 12, the vehicle-mounted device 100 waits in standbyuntil the first block of guide information transmitted from thedistribution center 200 for the split-download in response to therequest issued in step S257 is received or the guide informationtransmitted in a batch from the distribution center 200 in response tothe request issued in step S259. Upon deciding in step S261 that therequested guide information has been received, the guide processingstarts in step S263 based upon the guide information having beenreceived in step S261. The information having been received is storedinto the RAM 115 at the vehicle-mounted device 100. In step S265, adecision is made as to whether or not all the information necessary toprovide the route guidance has been received. If it is decided in stepS265 that all the information needed to provide the route guidance hasbeen received, the operation proceeds to step S281 to continuouslyexecute the guide processing based upon the received guide information.In step S283, the operation waits in standby for the completion of theguide processing. Upon deciding in step S283 that the guide processinghas ended, the operation returns to the main routine to end the mainroutine program.

If it is decided in step S265 that there is still information needed forthe route guidance that has not been received yet, the operationproceeds to step S267 to output a request for the distribution center200 to transmit the next block of guide information.

In response to the distribution request received from thevehicle-mounted device 100, the request receiving server 201 issues arequest for the yet-to-be transmitted guide information stored at thecustomer DB server 204 in step S63. In response to the request from therequest receiving server 201 received in step S85, i.e., in response tothe distribution request from the vehicle-mounted device, the customerDB server 204 transmits a divided block of the yet-to-be transmittedguide information stored therein to the request receiving server 201 instep S87. The request receiving server 201 transmits the yet-to-betransmitted guide information having been received from the customer DBserver to the vehicle-mounted device 100 in step S65.

In step S269 in FIG. 12, the vehicle-mounted device 100 waits in standbyuntil the guide information having been requested in step S267 isreceived. After deciding in step S269 that the requested guideinformation has been received, the guide processing is continuouslyexecuted based upon the received guide information in step S271 beforethe operation returns to step S265. Subsequently, the processing insteps S267 through S271 and the processing in steps S63 and S65 andsteps S85 and S87 are repeatedly executed respectively at thevehicle-mounted device 100 and the distribution center 200 as describedabove, until all the divided blocks of guide information are downloadedat the vehicle-mounted device 100. Namely, the vehicle-mounted device100 requests the yet-to-be received guide information in the backgroundwhile continuously executing the guide processing based upon thereceived guide information, as shown in FIG. 14, whereas thedistribution center 200 repeatedly transmits a divided block of guideinformation each time the yet-to-be received information distributionrequest from the vehicle-mounted device 100 is received until all theguide information is received at the vehicle-mounted device 100.

The following advantages are achieved through the first embodiment.

-   (1) Based upon the guide information size and the estimated download    time indicated at the display monitor 119, the user is able to    decide whether or not to receive the guide information in a split    download. As a result, if the user wishes to depart the start point    immediately by following the route guidance provided by the    vehicle-mounted device 100, the user is able to ensure that the    route guidance by the vehicle-mounted device 100 becomes available    as soon as the guide information corresponding to an area around the    current vehicle position is downloaded by opting for a split    download.-   (2) By opting for a split-download when the guide information size    is large and the estimated download time is significant, the risk of    an increased communication time due to a possible communication    failure/retry that may occur during a batch download can be avoided,    and the total length of time required for the download can be    reduced.-   (3) By opting for a split-download when the user driving the vehicle    between tall buildings or in a mountainous area judges that the    reception is poor, the risk of an increased communication time due    to a possible communication failure/retry that may occur during a    batch download can be avoided, and the total length of time required    for the download can be reduced.-   (4) By opting for a batch download when the guide information size    is small and the estimated download time is short, the user is able    to use the portable telephone 150 immediately by disconnecting it    from the vehicle-mounted device 100 after the guide information    download ends.-   (5) Even when the guide information size is large and the estimated    download time is significant, the risk of a communication failure is    low if the vehicle is in a stationary state and the reception is    good. Under such circumstances, the user may opt for a batch    download to reduce the download time.

Second through seventh embodiments of the information terminal accordingto the present invention are explained below. The structures shown inFIGS. 1 through 4 and 6 are also adopted in these embodiments and thefollowing explanation focuses on the contents of the subroutinesexecuted in the embodiments.

Second Embodiment

The information initially transmitted from the distribution center 200to the vehicle-mounted device 100 includes information indicating thenumber of guidance-requiring intersections contained in the guideinformation, as well as the route information in the second embodiment.Based upon the number of guidance-requiring intersections contained inthe guide information and the estimated download time calculated by thevehicle-mounted device 100, the user is able to decide whether or notthe yet-to-be received guide information should be received through asplit download. The following is an explanation of the secondembodiment.

The vehicle-mounted device 100 transmits to the distribution center 200information indicating the current vehicle position and the destinationand the route search condition determined through the subroutinesexecuted in step S100 together with the ID number to be used to identifythe vehicle. As explained earlier, the distribution center 200 accessesthe search•guide server 203 to execute a route calculation in step S700.

FIG. 15 shows the subroutine executed in step S700 in the secondembodiment. As the search•guide server 203 receives the route searchrequest from the request receiving server 201 in step S71 in FIG. 5, theoperation proceeds to step S700. In step S701 b, the route searchcalculation is executed based upon the position information and theroute search condition having been transmitted from the vehicle-mounteddevice 100. In step S703 b, a route coordinate string is extracted fromthe recommended route resulting from the route search calculation. Instep S705 b, data indicating the number of guidance-requiringintersections are extracted from the results of the calculation havingbeen executed in step S701 b. In step S707 b, the data indicating thenumber of guidance-requiring intersections obtained in step S705 b areappended to the route information (the route coordinate string datahaving been obtained in step S703 a) to be transmitted to thevehicle-mounted device 100 in the initial installment, before theoperation returns to the main routine. Then, in step S73 in the mainroutine, the route information and the guide information obtainedthrough the arithmetic operations executed in the subroutine in stepS700 are transmitted to the request receiving server 201.

The request receiving server 201 executes steps S57 through S61 in FIG.5, as in the first embodiment. In step S61, it transmits the routeinformation having attached thereto the data indicating the number ofguidance-requiring intersections to the vehicle-mounted device 100.

At the vehicle-mounted device 100, upon deciding in step S11 that theroute information has been provided by the distribution center 200 hasbeen received, the operation proceeds to the subroutine in step S200.

The subroutine executed in step S200 in the second embodiment isidentical to the subroutine in FIG. 12 executed in the first embodiment.However, the method with which the estimated download time fordownloading the yet-to-be received guide information is calculated instep S251 is different from that adopted in the first embodiment. In thesecond embodiment, the effective download speed with which the routeinformation has been downloaded is first calculated by dividing the sizeof the route information received from the distribution center 200 bythe length of time spent downloading the route information. Next, apredetermined information size corresponding to a singleguidance-requiring intersection is multiplied with the number ofguidance-requiring intersections indicated in the received data toestimate the size of the yet-to-be received guide information. Then, theestimated download time is calculated by dividing the estimated size ofthe yet-to-be received guide information by the effective downloadspeed.

In step S253, the route information having been received in step S11 andthe estimated download time having been calculated in step S251 arebrought up on display at the display monitor 119. FIG. 16 shows thescreen brought up on display at the display monitor 119 in step S253. Asshown in FIG. 16, a bold line 301 b indicating the recommended route anda dialogue 302 b asking the user whether or not the yet-to-be receivedguide information is to be split-downloaded are displayed at the displaymonitor 119. Through the dialogue 302 b, which includes indicating thenumber of guidance-requiring intersections and the estimated downloadtime having been calculated in step S251 the user is asked whether ornot he wishes to split-download the guide information.

Since the operation executed in step S255 and subsequent steps iscompletely identical to the operation executed in step S255 andsubsequent steps in the subroutine in the first embodiment, itsexplanation is omitted.

Third Embodiment

In the third embodiment, depending upon the state of radio wavesexchanged between the portable telephone 150 and the mobilecommunication network 250, a decision is made as to whether or not thevehicle-mounted device 100 is to receive the yet-to-be received guideinformation from the distribution center 200 in a split download. If theeffective speed with which the route information has been downloaded isequal to or lower than a predetermined threshold value, it is judgedthat the radio wave state (reception) is poor and accordingly, thevehicle-mounted device opts for a split download, whereas if theeffective speed with which the route information has been downloaded ishigher than the predetermined threshold value, the reception is judgedto be good and accordingly, the user is allowed to decide whether or notthe guide information is to be received through a split download, as hasbeen explained in reference to the first embodiment and the secondembodiment. The following is an explanation of the third embodiment.

At the vehicle-mounted device 100, upon deciding in step S11 that theroute information transmitted from the distribution center 200 as in thefirst and second embodiments explained earlier has been received, theoperation proceeds to the subroutine in step S200.

FIG. 17 shows the subroutine executed in step S200 in the thirdembodiment. Since the subroutine shown in FIG. 17 is substantiallyidentical to the subroutine in FIG. 12 executed in the first embodiment,the subroutine is explained by assigning reference numeralscorresponding to those in the subroutine executed in the firstembodiment. Namely, step S251 c in the subroutine executed in step S200in the third embodiment, for instance, corresponds to step S251 in thesubroutine executed in step S200 in the first embodiment. In step S211c, the effective speed with which the route information has beendownloaded is calculated. Namely, the effective speed with which theroute information has been downloaded is calculated by dividing the sizeof the route information having been received from the distributioncenter 200 by the length of time spent downloading the routeinformation.

In step S213 c, the effective speed having been calculated in step S211c is compared with the predetermined threshold value. If it is decidedin step S213 c that the effective speed is equal to or lower than thethreshold value, the operation proceeds to step S215 c to bring up amessage indicating that due to poor reception, a split-download is to beexecuted on display at the display monitor 119, as shown in FIG. 18.Then, the operation proceeds to step S257 c to transmit to thedistribution center 200 a split-download request for receiving theyet-to-be received guide information through a split download. Since theoperation executed in step S257 c and subsequent steps is identical tothe operation executed in step S257 and subsequent steps in the firstembodiment, its explanation is omitted.

If it is decided in step S213 c that the effective speed is not equal toor lower than the threshold value, the operation proceeds to step S251 cto calculate the estimated download time for downloading the yet-to-bereceived guide information. Since the operation executed in step S251 cand subsequent steps is identical to the operation executed in step S251and subsequent steps in the first embodiment or in step S251 b andsubsequent steps in the second embodiment, its explanation is omitted.

The following advantage is achieved through the third embodiment. Whenthe reception is poor, the risk of a communication failure occurringwhile a batch download is in progress to result in a repeatedretransmission/reception is significant. In particular, thecommunication tends to become cut off readily if the recipient vehicleengaged in communication is moving. If the communication is cut offduring a batch download, the information must be retransmitted/receivedfrom the beginning, and thus, the batch download will turn out to bemore time-consuming than a split download. As described above, thevehicle-mounted information terminal achieved in the third embodiment iscapable of making a decision as to whether or not to opt for asplit-download of the yet-to-be received guide information from thedistribution center 200 at the vehicle-mounted device 100 based upon thestate of radio waves exchanged between the portable telephone 150 andthe mobile communication network 250. Namely, if the reception is poor,the guide information being distributed is received through a splitdownload. (3) As a result, the risk of an increased communication timedue to a possible communication failure/retry that may occur during abatch download can be avoided, and the total length of time required forthe download can be reduced.

While the decision as to whether or not the reception is poor is madebased upon the effective speed with which the route information has beendownloaded in the third embodiment described above, this decision mayinstead be made based upon the electrical field intensity of a signalreceived at the portable telephone 150.

Fourth Embodiment

In the fourth embodiment, when a request for a route search istransmitted from the portable telephone 150 to the distribution center200, a decision is made at the vehicle-mounted device 100 based upon thedistance between the current vehicle position and the destination as towhether or not a request for a split-download of guide informationshould be requested. The following is an explanation of the fourthembodiment.

FIG. 19 presents a flowchart of the subroutine executed instep S100 inthe fourth embodiment. As the current vehicle position is indicated atthe display monitor 119 as shown in FIG. 6 in step S7 in the mainroutine shown in FIG. 5, the operation proceeds to step S100 to executethe subroutine. In step S101 d, the operation waits in standby until adestination is set through a user operation. FIG. 8 shows a displaybrought up on the display monitor 119 when the destination is set, withthe destination indicated as a cross point 402 of two lines runningperpendicular to each other at the display monitor 119. If it is decidedin step S101 d that a destination has been set, the distance between thecurrent vehicle position and the destination is calculated in step S151d. While the distance between the current vehicle position and thedestination changes depending upon the route that is selected, thedistance is calculated in this step as the length of a straight lineconnecting the vehicle position and the destination.

In step S153 d, a decision is made as to whether or not the distancebetween the current vehicle position and the destination is equal to orgreater than a predetermined threshold value. If it is decided in stepS153 d that the distance between the current vehicle position and thedestination is equal to or greater than the predetermined thresholdvalue, a split-download mode is set in the route search request from thevehicle-mounted device 100 so as to have the distribution center 200transmit the route search results in installments in step S155 d, andthen the operation proceeds to step S103 d. If, on the other hand, it isdecided in step S153 d that the distance between the current vehicleposition and the destination is less than the predetermined thresholdvalue, a batch download mode is set in the route search request from thevehicle-mounted device 100 so as to have the distribution center 200transmit the route search results all at once in a batch in step S157 d,and then the operation proceeds to step S103 d. It is to be noted thatthe user may be allowed to select the download mode as in the first andsecond embodiments.

In step S103 d, the route search condition setting screen in FIG. 9 isbrought up on display. After judging in step S105 d that the searchcondition has been set, the message indicating that the search is inprogress, as shown in FIG. 8, is brought up on display at the displaymonitor 119, before the operation proceeds to step S111 d. Upon decidingin step S111 d that the search condition having been set by the userthrough steps S103 d to 105 d gives priority to toll roads, theoperation proceeds to step S113 d. In step S113 d, the route searchrequest indicating the current position, the destination and the searchcondition giving priority to toll roads is transmitted to thedistribution center 200 in the download request mode having beendetermined through the processing in steps S153 d through 157 d, beforethe operation returns to the main routine to execute step S11 andsubsequent steps in the main routine. Since the processing executed inthe subroutine in FIG. 19 after making a decision in step S111 d thatthe search condition having been set by the user in steps S103 d through105 d does not give priority to toll roads is similar to the processingexecuted in step S121 and subsequent steps in the first embodiment, itsexplanation is omitted.

The information indicating the current vehicle position, the destinationand the route search condition selected through the subroutine and thedownload request mode is thus transmitted to the distribution centertogether with the ID number to be used to identify the vehicle. Thedistribution center 200 then accesses the search•guide server 203 toexecute a route calculation in step S700.

FIG. 20 shows the subroutine executed in step S700 in the fourthembodiment. As the route search request from the request receivingserver 201 is received at the search•guide server 203 in step S71 inFIG. 5, the operation proceeds to step S700. In step S701 d, a routesearch calculation is executed based upon the position information andthe route search condition indicated in the information transmitted fromthe vehicle-mounted device 100, and then the operation returns to themain routine. Then, in step S73 in the main routine, the routeinformation and the guide information obtained through the arithmeticoperations executed in the subroutine in step S700 are transmitted tothe request receiving server 201.

As explained earlier, the calculation results received from thesearch•guide server 203 are first transmitted to the customer DB server204 by the request receiving server 201 in step S59, and then theoperation proceeds to step S61. In step S61, the calculation resultsprovided by the search•guide server 203 are transmitted in the downloadmode having been requested by the vehicle-mounted device 100. Namely, ifa split-download has been requested by the vehicle-mounted device 100,the route information and part of the guide information are taken outfrom the results of calculations executed at the search•guide server 203and are transmitted to the vehicle-mounted device 100. If, on the otherhand, a batch download has been requested by the vehicle-mounted device100, the results of the calculations executed at the search•guide server203 are transmitted to the vehicle-mounted device 100 in a batch.

At the vehicle-mounted device 100, upon deciding in step S11 that theroute information from the distribution center 200 has been received,the operation proceeds to execute the subroutine in step S200.

FIGS. 21 and 23 show the subroutine executed in step S200 in the fourthembodiment. FIG. 21 shows the subroutine executed in step S200 when thesplit-download mode has been selected, whereas FIG. 23 shows thesubroutine executed in step S200 when the batch download mode has beenselected. The subroutines shown in FIGS. 21 and 23 are now explained byusing step numbers corresponding to the step numbers included in thesubroutine executed in the first embodiment. Namely, step S251 d in thesubroutine executed in step S200 in the fourth embodiment, for instance,corresponds to step S251 in the subroutine executed in step S200 in thefirst embodiment.

First, the subroutine shown in FIG. 21, which is executed in step S200when the split-download mode has been selected, is explained. At thevehicle-mounted device 100, upon deciding in step S11 that the routeinformation and guide information up to, for instance, the first guidepoint have been received from the distribution center 200, the operationproceeds to step S281 d to bring up at the display monitor 119 a messageindicating that a split-download is to be executed as shown in FIG. 22,and then the operation proceeds to step S263 d to start guide processingbased upon the guide information having been received. The operationexecuted in step S265 d in which a decision is made as to whether or notthe entire guide information has been received and subsequent steps isidentical to the operation executed in step S265 and subsequent steps inthe first embodiment, and for this reason, its explanation is omitted.

Next, the subroutine shown in FIG. 23, which is executed in step S200when the batch download mode has been selected, is explained. At thevehicle-mounted device 100, upon deciding in step S11 that the routeinformation and the guide information from the distribution center 200have been received in their entirety, the operation proceeds to stepS291 d to start guide processing based upon the guide information havingbeen received. In step S293 d, the operation waits in standby for thecompletion of the guide processing. Upon deciding in step S293 d thatthe guide processing has been completed, the operation returns to themain routine to end the main routine program.

The following advantage is achieved in the fourth embodiment. When thedistance between the current vehicle position and the destination islarge, the volume of the information that needs to be downloaded isbound to be large. If the communication fails while a batch download isin progress under these circumstances, the information will need to beretransmitted/received from scratch. As a result, the length of timerequired for the batch download may become greater than the length oftime that would be spent downloading the same information ininstallments. As explained earlier, at the vehicle-mounted device 100embodying the vehicle-mounted information terminal in the fourthembodiment, a decision can be made as to whether or not a split-downloadof the guide information should be requested based upon the distancebetween the current vehicle position and the destination when sending aroute search request from the portable telephone 150 to the distributioncenter 200. Namely, if the distance between the current vehicle positionand the destination is large, the guide information provided by thedistribution center is received through a split download. By opting fora split-download, the risk of an increased communication time due to apossible communication failure/retry that may occur during a batchdownload can be avoided, and the total length of time required for thedownload can be reduced.

Fifth Embodiment

In the fifth embodiment, when a route search request is transmitted fromthe portable telephone 150 to the distribution center 200, a decision ismade at the vehicle-mounted device 100 as to whether or not to request asplit-download of the guide information in correspondence to thespecific type of portable telephone 150 connected to the vehicle-mounteddevice 100. Namely, depending upon whether or not the portable telephone150 is capable of supporting high-speed communication, a decision ismade at the vehicle-mounted device 100 as to whether or not to request asplit-download of the guide information. The following is an explanationof the fifth embodiment.

FIG. 24 presents a flowchart of the subroutine executed in step S100 inthe fifth embodiment. As the current vehicle position is indicated atthe display monitor 119 as shown in FIG. 6 in step S7 in the mainroutine shown in FIG. 5, the operation proceeds to step S100 to executethe subroutine. In step S161 f, the type, i.e., the communication speedof the portable telephone 150 connected to the vehicle-mounted device100 is determined. If it is decided in step S161 f that thecommunication speed of the portable telephone 150 connected to thevehicle-mounted device 100 is equal to or higher than 28.8 kbps, theoperation proceeds to step S163 f to set the batch download mode in theroute search request to be issued by the vehicle-mounted device 100 soas to have the distribution center 200 transmit the route search resultsin a batch. If, on the other hand, it is decided in step S161 f that thecommunication speed of the portable telephone 150 connected to thevehicle-mounted device 100 is not equal to or higher than 28.8 kbps, theoperation proceeds to step S165 f to set the split-download mode in theroute search request to be output from the vehicle-mounted device 100 soas to have the distribution center 200 transmit the route search resultsin installments.

Since the processing executed in step S101 f and subsequent steps in thesubroutine in FIG. 24 is similar to the processing executed in step S101d and subsequent steps in the subroutine in the fourth embodiment, itsexplanation is omitted. In addition, since the operation at thedistribution center 200 executed after the vehicle-mounted device 100transmits the route search request to the distribution center 200 instep S100 and the operation at the vehicle-mounted device 100 havingreceived the information are also similar to those in the fourthembodiment, their explanation is omitted, as well. However, a messageindicating that a split-download is to be executed is brought up ondisplay at the display monitor 119 as shown in FIG. 25 in step S281 d inFIG. 21.

At the vehicle-mounted device 100 embodying the vehicle-mountedinformation terminal in the fifth embodiment, a decision can be made asto whether or not to request a split-download of the guide informationbased upon the type of the portable telephone 150 connected to thevehicle-mounted device 100. Namely, if the portable telephone 150 iscapable of supporting high-speed communication, the guide information isreceived in a batch download, whereas if the portable telephone does notsupport high-speed communication, the guide information provided by thedistribution center is received through a split download. As a result,the communication can be completed quickly through a batch download ifthe portable telephone connected to the vehicle-mounted device 150supports high-speed communication. If, on the other hand, the portabletelephone connected to the vehicle-mounted device 150 does not havehigh-speed communication capability, the information is received througha split-download so as to eliminate the risk of an increase in thecommunication time caused by a communication failure/retry which mayoccur during a batch download and thus to reduce the overall downloadtime.

Sixth Embodiment

In the sixth embodiment, when a route search request for thedistribution center 200 to search for a route to a destination is alsotransmitted from the portable telephone 150, information indicating thedestination and a plurality of waypoints is transmitted and thedistribution center 200 is requested to transmit both the recommendedroute information and the guide information resulting from the routesearch calculation executed at the distribution center 200 incorrespondence to each waypoint. Namely, the route search calculationresults corresponding to the part of the route from the current positionto the first waypoint are initially received, the route search resultscorresponding to the part of the route to the next waypoint are receivedas the vehicle reaches the area near the first waypoint and thesubsequent route guidance is provided based upon the route searchresults received in sequence. The operation executed in the sixthembodiment is now explained.

FIG. 26 shows the subroutine executed in step S100 in the sixthembodiment. As the current vehicle position is indicated at the displaymonitor 119 as shown in FIG. 6 in step S7 of the main routine shown inFIG. 5, the operation proceeds to step S100 to execute the subroutine.In step S161 g, a request mode to indicate how the recommended routeinformation and the guide information resulting from the route searchcalculation executed at the distribution center 200 are to be receivedis selected.

The mode selected in step S161 g is either a split route guidancerequest mode or a split route search calculation mode. If the splitroute guidance request mode is selected, the vehicle-mounted device 100and the distribution center 200 engage in operation as described below.

-   (1) The distribution center 200 executes a route search calculation    to determine the route to be taken from the start point (the subject    vehicle position) to the destination based upon the information    received from the vehicle-mounted device 100 and stores in memory    the calculation results.-   (2) The vehicle-mounted device 100 receives both the recommended    route information and the guide information resulting from the route    search calculation executed at the distribution center 200 in    correspondence to each block of the route cut off at a waypoint.    First, the calculation results corresponding to the block extending    from the start point to the first waypoint are received. The route    guidance is started based upon the received calculation results, and    as the vehicle approaches the first waypoint, a request for the    distribution center 202 to transmit the route search calculation    results corresponding to the block extending to the next waypoint,    which are stored at the distribution center 200, is automatically    issued. The route search calculation results are thus received in    sequence until the results corresponding to the last block extending    to the destination are received.

The vehicle-mounted device 100 and the distribution center 200 engage inoperation as described below when the split route search calculationmode is selected.

-   (1) The distribution center 200 executes a route search calculation    to determine the route from the start point (the subject vehicle    position) to the first waypoint based upon the information received    from the vehicle-mounted device 100 and stores in memory the    calculation results.-   (2) The vehicle-mounted device 100 receives both the recommended    route information and the guide information resulting from the route    search calculation having been executed to determine the route to    the first waypoint. Then, the vehicle-mounted device starts the    route guidance, and as the vehicle approaches the first waypoint,    the driver is prompted to indicate whether or not to search for the    route to the next waypoint. If the driver indicates that a route    search is to be executed to determine the route to the next    waypoint, a request for the execution of the route search    calculation up to the next waypoint and the transmission of the    calculation results is issued to the distribution center 200. Thus,    the route search calculation request is issued in correspondence to    each waypoint and the calculation results are received in sequence.

Namely, unlike in the split route guidance request mode, thedistribution center 200 does not execute a route search calculation forthe entire route but instead it executes a route search calculation forthe block extending from the current vehicle position to the nextwaypoint only and transmits the calculation results to thevehicle-mounted device 100 in the split route search calculation mode.

If it is decided in step S161 g that the selected request mode is thesplit route guidance request mode, the operation proceeds to step S163 gto set the split route guidance request mode before proceeding to stepS101 g. If it is decided in step S161 g that the selected request modeis the split route search calculation mode, the operation proceeds tostep S165 g to set the split route search calculation mode beforeproceeding to step S101 g. Then, in step S101 g, the operation waits instandby for the destination and the waypoints to be set through useroperation. It is to be noted that if no waypoint is set, the calculationis executed by designating the first waypoint to be detailed later asthe destination. Upon judging in step S101 g that the destination andthe waypoints have been set, the operation proceeds to step S103 g.Since the processing executed in step S103 g and subsequent steps in thesubroutine in FIG. 26 is similar to that executed in step S103 d andsubsequent steps in the subroutine in the fourth embodiment, itsexplanation is omitted.

The information indicating the current vehicle position and thedestination, the waypoints, the route search condition and the requestmode selected through the subroutine, is transmitted to the distributioncenter 200 together with the ID number used to identify the vehicle. Asexplained earlier, the distribution center 200 accesses the search•guideserver 203 to execute the route search calculation. The calculationresults are transmitted to the vehicle-mounted device 100 via therequest receiving server 201.

While the processing executed at the distribution center 200 is notexplained in detail, it may be summarized as follows. If the split routeguidance request mode has been selected at the vehicle-mounted device100, the information transmitted from the request receiving server 201in step S61 in FIG. 5 includes the recommended route information and theguide information for the block extending to the first waypoint, whichconstitute part of the results of the route search calculation executedto determine the route to the destination. In addition, the informationtransmitted from the request receiving server 201 to the vehicle-mounteddevice 100 in step S65 taken out from the results of the route searchcalculation having been executed to determine the route to thedestination, includes the recommended route information and the guideinformation for the block extending to the next waypoint or thedestination beyond the waypoint in correspondence to which informationhas been transmitted to the vehicle-mounted device 100 most recently.

If the split route search calculation mode has been selected at thevehicle-mounted device 100, the information transmitted from the requestreceiving server 201 to the vehicle-mounted device 100 in step S61 inFIG. 5 includes the recommended route information and the guideinformation indicated by the results of the route search calculationhaving been executed to determine the route to the first waypoint.Subsequently, each time a route search calculation request transmittedthrough the subroutine executed at the vehicle-mounted device 100 instep S200 as described later is received at the distribution center 200,a route search calculation is executed to determine the route to thenext waypoint or the destination beyond the waypoint in correspondenceto which information has been transmitted to the vehicle-mounted device100 most recently and the recommended route information and the guideinformation resulting from the route search calculation are transmittedto the vehicle-mounted device 100.

FIG. 27 shows the subroutine executed in step S200 in the sixthembodiment. At the vehicle-mounted device 100, upon deciding in step S11in FIG. 5 that the recommended route information and the guideinformation corresponding to the block extending to the first waypoint,i.e., the route search information corresponding to the block up to thefirst waypoint, have been received from the distribution center 200, theoperation proceeds to step S281 g to bring up a message indicating thatthe route guidance up to the first waypoint is to be provided at thedisplay monitor 119, as shown in FIG. 28, and then the operationproceeds to step S263 g. FIG. 28 shows a display brought up at thedisplay monitor 119, which includes a dialogue 303 g indicating thatroute guidance is to start and a recommended route 301 g to the firstwaypoint indicated by the route search information having been received.In step S263 g, guide processing starts based upon the received routesearch information.

In step S265 g, a decision is made as to all the route searchinformation including the block extending to the final destination hasbeen received. If a negative decision is made in step S265 g, theoperation proceeds to step S291 g to make a decision as to whether ornot the number of guide points for which guidance has not yet beenprovided, contained in the route search information having beenreceived, is equal to or smaller than one. If an affirmative decision ismade in step S291 g, the operation proceeds to step S293 g to make adecision as to whether or not the split route search calculation modehas been selected.

If an affirmative decision is made in step S293 g, i.e., if it is judgedthat the split route search calculation mode has been selected, theoperation proceeds to step S295 g. In step S295 g, a dialogue 304 gasking the user whether or not he wishes to receive the next set ofroute search information is brought up on display at the display monitor119 as shown in FIG. 29, and thus, the driver is prompted to indicatewhether or not he wishes to issue a request that the distribution center200 execute the route search calculation up to the next waypoint andtransmit the calculation results. A subject vehicle position mark 1 inFIG. 29 indicates that the vehicle is currently traveling along therecommended route 10 toward an intersection 11. Guide information suchas “turn left at the second intersection ahead” has already beenprovided with regard to the intersection 11, whereas no guideinformation has yet been provided with regard to an intersection 12beyond the intersection 11. In addition, touch panel switches 305 g to307 g through which the user is able to indicate whether or not toreceive the next set of route search information are displayed as partof the dialogue 304 g.

If the switch 305 g is pressed and accordingly, an affirmative decisionis made in step S297 g, i.e., if the user is judged to wish to issue arequest that the distribution center 200 execute a route searchcalculation for the next waypoint and transmit the calculation results,the operation proceeds to step S267 g. Instep S267 g, a request for theroute search calculation up to the next waypoint and the transmission ofthe calculation results is transmitted to the distribution center 200,before the operation proceeds to step S269 g. Since the processingexecuted in step S269 g and subsequent steps is similar to that executedin step S269 d and subsequent steps in the subroutine in the fourthembodiment, its explanation is omitted.

If the switch 305 g is not pressed and accordingly a negative decisionis made in step S297 g, the operation proceeds to step S298 g to make adecision as to whether or not the switch 306 g has been pressed. If itis decided in step S298 g that the switch 306 g has been pressed and anaffirmative decision is made accordingly, i.e., if it is judged that theuser does not wish to request the execution of the route searchcalculation up to the next waypoint or the transmission of thecalculation results, the operation proceeds to step S281 g. If theswitch 306 g has not been pressed and a negative decision is made instep S298 g, on the other hand, the operation proceeds to step S299 g tomake a decision as to whether or not the switch 307 g has been pressed.If the switch 307 g has been pressed and an affirmative decision is madein step S299 g, i.e., if it is decided that a search for another routeis to be executed, this subroutine ends and the operation returns tostep S3 in the main routine. If the switch 307 g has not been pressedand a negative decision is made in step S299 g, the operation returns tostep S297 g.

If an affirmative decision is made in step S265 g or an affirmativedecision is made in step S298 g, the operation proceeds to step S281 gto continuously execute the guide processing. Then, the operation waitsin standby for the guide processing to end in step S283 g. If anaffirmative decision is made in step S283 g, this subroutine ends.

If a negative decision is made in step S291 g, the operation proceeds tostep S271 g to continuously execute the guide processing, and then theoperation returns to step S265 g.

If a negative decision is made in step S293 g, i.e., if it is judgedthat the split route guidance request mode has been selected, theoperation proceeds to step S267 g to transmit a request for the routesearch information corresponding to the block extending to the nextwaypoint, and then the operation proceeds to step S269 g.

The following advantages are achieved in the sixth embodiment describedabove.

-   (1) If the entire route search information for the route to the    final destination is received at an early stage after the vehicle    starts toward the final destination and then the user decides to    take a different route part way through, the route search    information for the route beyond the point at which the route is    changed and the corresponding communication cost will be wasted. In    contrast, by receiving the route search information in smaller    installments as in the sixth embodiment, the user does not need to    incur the communication cost for downloading the route search    calculation results for the remainder of the route if the driver    changes his mind and decides to travel on a different route.-   (2) When the split route guidance request mode has been selected,    the vehicle-mounted device 100 requests the route search calculation    results corresponding to the block extending to the next waypoint    from the distribution center 200 as the subject vehicle approaches    the immediate waypoint and is able to continuously provide the route    guidance by using the received route search calculation results.    Thus, another advantage is achieved in that the vehicle is guided    smoothly without inconveniencing the driver, in addition to the    advantage described above.-   (3) When the split route search calculation mode has been selected,    the vehicle-mounted device 100 prompts the driver to indicate    whether or not to request the route search calculation results for    the block extending to the next waypoint from the distribution    center 200 as the subject vehicle approaches the immediate waypoint.    The driver, thinking that he will probably want to take another    route near the waypoint, may select this mode when departing for the    destination. In the split route search calculation mode, the driver    is allowed to choose to request the route search calculation results    for the block extending to the next waypoint from the distribution    center 200 or to request a search of a different route by the    distribution center 200. As a result, the user does not need to    incur the communication cost for downloading the route search    calculation results for the block to the next waypoint that would be    automatically received in the split route guidance request mode and,    at the same time, a higher level of convenience for the driver is    assured. In addition, since no unnecessary arithmetic operation is    executed, the onus on the distribution center 200 is reduced as    well.

Seventh Embodiment

In the seventh embodiment, when issuing a request for the transmissionof remaining guide information to be received in an installment to thedistribution center 200, information indicating the average vehiclespeed per hour having been collected up to the time point at which therequest is transmitted in correspondence to each road type, too, istransmitted to the distribution center 200. At the distribution center200, guide information to be transmitted to the vehicle-mounted device100 is extracted based upon the average speed per hour informationtransmitted from the vehicle-mounted device 100 and transmits theextracted guide information to the vehicle-mounted device 100. Theoperation executed in the seventh embodiment is now explained. It is tobe noted that the following explanation focuses on the operation uniqueto the seventh embodiment and a full explanation of the seventhembodiment, which is otherwise identical to the first embodiment, is notprovided.

FIG. 31 shows the subroutine executed in step S200 in the seventhembodiment. At the vehicle-mounted device 100, upon deciding in step S11in FIG. 5 that the route information and the guide information for theblock extending to the first guide have been received from thedistribution center 200, the estimated download time for downloading theentire guide information is calculated in step S251 i. Since thesubsequent processing executed in steps S251 i through S265 i isidentical to the processing executed in the first embodiment in stepsS251 through S265 as explained in reference to FIG. 12, its explanationis omitted.

In step S265 i, a decision is made as to whether or not the entire guideinformation has been received. If a negative decision is made in stepS265 i, the operation proceeds to step S291 i to make a decision as towhether or not the number of guide points for which guidance isyet-to-be provided is equal to or smaller than one. If a negativedecision is made in step S291 i, the operation proceeds to step S271 ito continuously execute the guide processing before the operationreturns to step S265 i. If, on the other hand, an affirmative decisionis made in step S291 i, the operation proceeds to step S292 i tocalculate the average speeds per hour respectively for regular roads andexpress highways having been traveled up to the current time point, andthen the operation proceeds to step S267 i. In step S267 i, a requestfor the next set of guide information is transmitted to the distributioncenter 200 together with information indicating the average speeds perhour for the regular roads and the express highways having beencalculated in step S292 i, and then the operation proceeds to step S269i. Since the processing executed in step S269 i and subsequent steps issimilar to the processing executed in step S269 and subsequent steps inthe subroutine in the first embodiment, its explanation is omitted.

While the operation proceeds to step S281 i after making an affirmativedecision in step S265 i, the operation executed in step S281 i andsubsequent steps is identical to that executed in step S281 andsubsequent steps in the first embodiment and, for this reason, itsexplanation is omitted.

FIG. 32 presents an integrated flowchart of the operations executed atthe vehicle-mounted device 100, the request receiving server 201, thesearch•guide server 203 and the customer DB server 204 in the seventhembodiment. It is to be noted that since the operation executed at thevehicle-mounted device 100 in steps S1 through S11, the operationexecuted at the request receiving server 201 in steps S51 through S61,the operation executed at the search•guide server 203 in steps S71through S73 and the operation executed at the customer DB server 204 insteps S81 through S83 are identical to the corresponding operationsexecuted in the first embodiment, their explanation is omitted.

In response to a distribution request received from the vehicle-mounteddevice 100 instep S63 i, the request receiving server 201 issues arequest that the guide information stored in the customer DB server 204be transmitted to the search•guide server 203, before proceeding to stepS64 i. In step S64 i, the request receiving server transmits theinformation indicating the average speeds per hour for the regular roadsand the express highways and the current vehicle position having beenreceived in step S63 i from the vehicle-mounted device 100 to thesearch•guide server 203. In step S65 i, it transmits the guideinformation received from the search•guide server 203 as explained laterto the vehicle-mounted device 100.

At the customer DB server 204, in response to the request having beenreceived from the request receiving server 201 in step S85 i, i.e., inresponse to the distribution request issued from the vehicle-mounteddevice 100, the guide information for the entire route having beenstored in step S83 is transmitted to the search•guide server 203 in stepS87 i.

At the search•guide server 203, the position to which the vehicle willhave traveled after a predetermined length of time (hereafter referredto as the calculated vehicle position) is ascertained through anarithmetic operation and the guide information to be used to guide thevehicle to the calculated vehicle position is extracted in step S77 ibased upon the information indicating the average speeds per hour andthe current vehicle position having been received from thevehicle-mounted device 100 in step S75 i and the entire guideinformation having been received in step S76 i. In step S78 i, thesearch•guide server transmits the results of the arithmetic operationexecuted in step S77 i, i.e., the guide information for the blockextending to the calculated vehicle position, to the request receivingserver 201.

The following advantages are achieved in the seventh embodiment.

-   (1) Based upon the past average speed per hour information    transmitted thereto, the distribution center 200 is able to estimate    the point at which the vehicle equipped with the vehicle-mounted    device 100 will be located after a predetermined length of time and    set the guide information for the block extending to the particular    point as the guide information to be transmitted next. As a result,    a guide information request is generated from the vehicle-mounted    device 100 over substantially constant time intervals. Since this    allows the driver to anticipate when the next guide information    request will be generated, he is able to avoid unnecessarily    incurring the communication cost for downloading the guide    information that has not been received yet, should he change his    mind and decide to travel on a different route.-   (2) Since the average speeds per hour for regular roads and express    highways are both calculated and thus the average speed per hour    closely reflecting the actual traveling state can be ascertained,    the calculated vehicle position can be determined with a high level    of accuracy so as to allow the correct volume of information to be    set to be transmitted to the vehicle-mounted device 100.

Variations of the First Through Seventh Embodiments

While the user is prompted to indicate whether or not to receiveinformation through a split-download in the display screen at thevehicle-mounted device 100 that has received the route informationhaving attached thereto information indicating the guide informationsize or the route information having attached thereto informationindicating the number of guidance-requiring intersections in the first,second and seventh embodiments, the decision as to whether or not to optfor a split-download may be automatically made by the vehicle-mounteddevice 100.

For instance, after calculating the estimated download time for theyet-to-be received guide information in step S251 in the firstembodiment, the estimated download time may be compared with apredetermined threshold value. Then, the download mode indicated in theroute search request from the vehicle-mounted device 100 may be set soas to receive the guide information through a batch download if theestimated download time is smaller than the threshold value and toreceive the guide information through a split-download if the estimateddownload time is equal to or greater than the threshold value.

In a variation of the second embodiment, the decision as to whether ornot to select a split-download may be made by comparing the estimateddownload time with a predetermined threshold value as in the variationof the first embodiment, or the decision as to whether or not to selecta split-download may be made in a similar manner but based upon thenumber of guidance-requiring intersections instead of the estimateddownload time.

These variations allow the vehicle-mounted device 100 to determine theoptimal download method without involving the user to relieve the userof the onus of decision-making. In addition, once the destination andthe search condition are set, the user does not need to perform afurther operation at the vehicle-mounted device 100 and the user havingstarted driving the vehicle, for instance, is able to focus on drivingfor better safety.

While the quality of reception is judged at the vehicle-mounted device100 in the third embodiment, the reception may be judged at thedistribution center 200, instead.

While the decision as to whether or not to request a split-download ismade based upon the distance between the current vehicle position andthe destination in the fourth embodiment, the decision may be made bytaking into consideration the search condition, as well. For instance,even when the distance between the current vehicle position and thedestination is very large, the number of guidance-requiringintersections on the route determined under the search condition givingpriority to express highway traveling is bound to be small and the datasize of the guide information, too, will be small. In such a case, theguide information may be downloaded in a batch.

While the decision as to whether or not to request a split-download ismade in the fifth embodiment by as certaining whether or not thecommunication speed is equal to or higher than 28.8 kbps, acommunication speed value other than this may be used in thedecision-making.

In the sixth embodiment, as the subject vehicle approaches a givenwaypoint, the vehicle-mounted device 100 automatically issues a requestfor the route search calculation results corresponding to the blockextending to the next waypoint to the distribution center 200 in thesplit route guidance request mode. In addition, as the subject vehicleapproaches a waypoint, the vehicle-mounted device 100 prompts the driverto indicate whether or not to transmit to the distribution center 200 arequest for the route search calculation results corresponding to theblock extending to the next waypoint. However, the present invention isnot limited to this example. As the subject vehicle approaches awaypoint, the vehicle-mounted device 100 mode may prompt the driver toindicate whether or not to transmit to the distribution center 200 arequest for the route search calculation results corresponding to theblock extending to the next waypoint. In addition, as the subjectvehicle approaches a waypoint, the vehicle-mounted device 100 mayautomatically transmit to the distribution center 200 a request for theroute search calculation results corresponding to the block extending tothe next waypoint. Furthermore, the route search calculation results forthe block extending to the next waypoint may be automatically requestedin both modes, or the route search calculation results for the blockextending to the next waypoint may be requested only after verifyingwith the driver in both modes.

While the guide information extracted based upon the informationindicating the actual average speeds corresponding to individual typesof roads having been traveled, which has been transmitted from thevehicle-mounted device 100, is transmitted from the distribution center200 in the seventh embodiment, guide information extracted based uponaverage speeds corresponding to different types of roads which are setin advance at the distribution center 200 may instead be transmittedfrom the distribution center 200. The range of guide information to betransmitted may be determined by taking into consideration the trafficconditions on the recommended route. Namely, the distribution center 200may obtain road state data managed by the Road Administration Departmentin individual regions to ascertain the average speed along therecommended route with better accuracy, and the size of the guideinformation to be transmitted may be determined based upon the averagespeed thus ascertained. It is to be noted that the present invention isnot limited to this example. As in the sixth embodiment, both therecommended route information and the guide information, i.e., the routesearch information, may be transmitted over the range determined incorrespondence to the average speed.

While the information initially transmitted from the distribution center200 for a split-download only contains the route information or theroute information having attached thereto information indicating thedata size of the guide information or information indicating the numberof guidance-requiring intersections in the first to fifth embodiments,the seventh embodiment and the variations of embodiments describedabove, a small volume of the guide information itself may also betransmitted. For instance, through the route calculation executed instep S700 at the search•guide server 203, guide information for a blockextending to the first guidance-requiring intersection distanced fromthe current position by a value larger than a predetermined thresholdvalue may be extracted. Then, the information initially transmitted tothe vehicle-mounted device 100 may include the route information and theguide information thus extracted. In addition, if a route search requestgiving priority to express highway traveling has been issued from thevehicle-mounted device 100 and there is an entrance to an interchange ata point closer to the current position than the first guidance-requiringintersection distanced from the current position by a value larger thanthe threshold value, the information initially transmitted to thevehicle-mounted device 100 may include the route information and guideinformation corresponding to the block extending to the interchangeentrance. By adopting this variation, in which the vehicle-mounteddevice 100 receives the guide information over a certain distancetogether with the route information once the destination and the searchcondition are set, the route guide can be started immediately.

While the decision as to whether or not information is to be received ina split-download is made by the user, the vehicle-mounted device 100 orthe distribution center 200 in the first through fifth embodiments, theseventh embodiment and the variations of embodiments described above,the user may set the vehicle-mounted device 100 for a split-download inadvance.

While the vehicle-mounted device 100 issues a request for thedistribution center 200 to distribute the next installment of guideinformation for a split-download when the reception of the precedinginstallment of guide information is completed in the first through fifthembodiments and the variations of embodiments explained above, thedistribution request may not be issued by the vehicle-mounted device 100immediately after receiving the preceding installment of guideinformation. For instance, the distribution request may be issuedimmediately after the vehicle has traveled through the lastguidance-requiring intersection included in the guide information havingalready been received. Alternatively, the distribution request may beissued when there is only one remaining guide point for which guidanceis yet-to-be provided, as in the sixth and seventh embodiments.Furthermore, in the sixth and seventh embodiments and the variationsthereof, the distribution request may be issued immediately after thevehicle has passed through the last guide point included in the routesearch information having already been received.

While the customer DB server 204 splits the guide information incorrespondence to individual guidance-requiring intersections or thecustomer DB server 204 splits the guide information so that a singleunit of split guide information corresponds to a plurality ofguidance-requiring intersections if the distances between the individualguidance-requiring intersections are short in the first through fifthembodiments and the variations of the embodiments described above, thepresent invention is not limited to this example. The guide informationmay be divided in units each corresponding to a waypoint present betweenthe start point and the destination, instead.

The individual embodiments and the variations thereof described abovemay be adopted in conjunction with one another.

In addition, the information transmitted from the distribution center200 in the embodiments and the variations thereof described above is notlimited to the route information and the guide information. Forinstance, real-time information such as weather information around thecurrent vehicle position and the destination, sale informationindicating sale prices at stores, information indicating the cherryblossom status or the autumn color status at scenic points, informationindicating crowd sizes at tourist attractions and natural disasterinformation may be transmitted. In addition, urgent information such asnatural disaster information may be transmitted from the distributioncenter 200 and a message indicating that urgent information has beenreceived may be brought up on display at the display monitor 119 of thevehicle-mounted device 100 without a request from the vehicle-mounteddevice 100.

INDUSTRIAL APPLICABILITY

While the present invention is adopted in a vehicle-mounted carnavigation device in the embodiments described above, the presentinvention may also be adopted in a portable navigation device. Inaddition, the present invention may be adopted in information terminalswith communication capabilities used for various purposes as well as innavigation devices. AS long as the features characterizing the presentinvention are not compromised, the present invention is in no wayrestricted to the structures adopted in the embodiments described above.

1.-15. (canceled)
 16. A route guidance method for providing routeguidance by exchanging information related to a recommended route from astart point to a destination between an information terminal and aninformation distribution center, comprising in sequence: (a) a step inwhich the information terminal transmits information indicating thestart point and the destination to the information distribution center;(b) a step in which the information distribution center obtains routeguide information for a route from the start point to the destinationthrough a search calculation; (c) a step in which when a state ofcommunication between the information terminal and the informationdistribution center is poor, the information distribution center splitsresults of the search calculation and transmits the search calculationresults to the information terminal in installments; and (d) a step inwhich when the search calculation results are transmitted ininstallments, the information terminal starts the route guidance uponreceiving, at least, search calculation results corresponding to an areanear the start point.
 17. A route guidance method for providing routeguidance by engaging an information terminal that transmits informationindicating a start point and a destination to an informationdistribution center and the information distribution center that obtainsthrough a search calculation route guide information for a route fromthe start point to the destination, splits results of the searchcalculation and transmits the search calculation results to theinformation terminal in installments when a predetermined conditionexists, comprising in sequence: (a) a step in which a user is informedof an estimated download time for downloading the search calculationresults, determined based upon a physical quantity indicating a size ofthe search calculation results; (b) a step in which the informationterminal transmits to the information distribution center informationindicating an instruction by the user that the information distributioncenter splits the search calculation results and transmits the searchcalculation results in installments; (c) a step in which upon receivingthe information indicating the instruction by the user that the searchcalculation results be split and transmitted in installments, theinformation distribution center extracts search calculation resultscorresponding to an area near the start point from the searchcalculation results and transmits the extracted search calculationresults; and (d) a step in which upon receiving the search calculationresults corresponding to the area near the start point, the informationterminal starts the route guidance.
 18. A route guidance methodaccording to claim 17, wherein: the search calculation results includeroute information of the route from the start point to the destinationand guide information used to indicate an advancing direction and thelike at each guide point on the route.
 19. A route guidance methodaccording to claim 18, wherein: the search calculation resultscorresponding to the area near the start point include at least guideinformation for a block extending from the start point to a next guidepoint.
 20. A route guidance method according to claim 17, wherein: thephysical quantity indicates a data size of the guide information or anumber of guide points contained in the guide information.
 21. A routeguidance method according to claim 17, wherein: after starting the routeguidance, the information terminal transmits to the informationdistribution center a request for remaining guide information.
 22. Aroute guidance method according to claim 21, wherein: the informationterminal transmits to the information distribution center a request thatthe remaining guide information be distributed in units eachcorresponding to a guide point; and each time the request is received,the information distribution center transmits guide informationextracted in a unit corresponding to a guide point to the informationterminal.
 23. A route guidance method for providing route guidance byexchanging information related to a recommended route from a start pointto a destination between an information terminal and an informationdistribution center, comprising in sequence: (a) a step in which theinformation terminal transmits information indicating the start pointand the destination to the information distribution center; (b) a stepin which the information distribution center obtains route guideinformation for a route from the start point to the destination througha search calculation; (c) a step in which when a distance between thestart point and the destination is equal to or greater than apredetermined value, the information distribution center splits resultsof the search calculation and transmits the search calculation resultsto the information terminal in installments; and (d) a step in whichwhen the search calculation results are transmitted in installments, theinformation terminal starts the route guidance upon receiving, at least,search calculation results corresponding to an area near the startpoint.
 24. A route guidance method for providing route guidance byexchanging information related to a recommended route from a start pointto a destination between an information terminal and an informationdistribution center, comprising in sequence: (a) a step in which theinformation terminal transmits information indicating the start pointand the destination to the information distribution center; (b) a stepin which the information distribution center obtains route guideinformation for a route from the start point to the destination througha search calculation; (c) a step in which when a communication devicewith a data transmission speed equal to or lower than a predeterminedvalue is connected to the information terminal, the informationdistribution center splits results of the search calculation andtransmits the search calculation results to the information terminal ininstallments; and (d) a step in which when the search calculationresults are transmitted in installments, the information terminal startsthe route guidance upon receiving, at least, search calculation resultscorresponding to an area near the start point.
 25. A route guidancemethod for providing route guidance by exchanging information related toa recommended route from a start point to a destination between aninformation terminal and an information distribution center, comprisingin sequence: (a) a step in which the information terminal transmitsinformation indicating the start point and the destination to theinformation distribution center; (b) a step in which the informationdistribution center obtains route guide information for a route from thestart point to the destination through a search calculation; (c) a stepin which the information distribution center transmits to theinformation terminal route information contained in results of thesearch calculation in a batch and transmits guide information containedin the results of the search calculation to the information terminal ininstallments by splitting the guide information; and (d) a step in whichthe information terminal starts the route guidance upon receiving theroute information included in the search calculation results and atleast guide information for an area near the start point included in thesearch calculation results and transmitted in an installment.